System and process for making synthetic wood products from recycled materials

ABSTRACT

A process for making synthetic wood products from waste wood fiber and recycled plastic material by mixing waste wood fiber having a moisture content of less than about 15% with dry waste plastic material, including low density and/or high density polyethylene; heating and kneading the mixture to form a homogeneous mass; sizing the mass into discrete chunks suitable for use as an extruder feed material; extruding the material to form products having predetermined cross sections; and rolling and cooling the product to prevent deformation of the product shape.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 07/491,061,filed Nov. 14, 1990, pending.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to a system and process for making syntheticwood products, such as building materials, including roof shingles,siding, floor tiles, paneling, moldings, structural components, steps,door and window sills and sashes; house and garden items, such asplanters, flower pots, landscape tiles, decking, outdoor furniture,fencing, and playground equipment; farm and ranch items, includingpasture fencing, posts and barn components; and marine items, forexample, decking, bulkheads and pilings, through a process whichcombines certain wood scrap material, such as cedar fiber waste, andplastic waste materials, such as high density polyethylene, low densitypolyethylene, polypropylene and mixtures thereof, and equivalentmaterials.

The starting wood and plastic materials are identified, processed,mixed, and then formed into building material products through use of anextruder and subsequent rolling processes to produce products which haveadvantages over natural wood and over other synthetic materials, suchthat products of the present invention are ordinarily less expensive;have excellent insulating properties; are highly resistant to insectinfestation, rotting, splitting, cracking, warping, thermal expansion orabsorption of moisture; can be easily shaped and machined; and, in manycases, have superior structural integrity.

2. Needs to Which the Present Invention is Directed

By current estimate, the United States generates half of the world'ssolid and industrial waste. By the year 2000, if present tends continue,the United States will be discarding 192.7 million tons per year. Onlyabout 22% of this waste is projected to be recycled. Landfills areutilized for the disposal of much of this waste. The United StatesEnvironmental Protection Agency (EPA) estimates that by the year 2000,75% of all existing landfills in the United States will be closed.

According to EPA statistics, discarded plastic presently constitutesabout 7.3 percent of the U.S. waste stream. Only about 1% of thisplastic waste is recycled. By the year 2000, production of plastics inthe U.S. is expected to reach 76 billion pounds per year, with discardedplastics expected to make up 10% of the waste stream by weight and up to1/3 by volume.

There is clearly a pressing need to adopt means by which plastics andother solid waste materials such as wood fiber waste can be recycledinto new and useful products. The present invention meets such need.

3. State of the Art Prior to the Present Invention

There have been developed numerous methods for combining waste woodmaterials and binders. Examples of such methods can be found in thepractice of pressboard and extrusion moulding technologies. However, ithas been observed that these methods are limited in the raw materialsthat can be utilized and in the quality and application of the productsproduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a top view of the preferred material preparation auger of thepresent invention.

FIG. 2 is an end view of the FIG. 1 auger.

FIG. 3 is a view of a blade of the FIG. 1 auger.

FIG. 4 is an exploded perspective view of the preferred extruder of thepresent invention.

FIG. 5 is a side view of the preferred flying cutoff assembly of thepresent invention.

FIG. 6 is a downstream end view of the FIG. 5 assembly with the knife ofthe flying cutoff in the down position.

FIG. 7 is a downstream end view of the FIG. 5 assembly with the knife ofthe flying cutoff in the up position.

FIG. 8 is a side view of the preferred rolling and cooling conveyor ofthe present invention.

FIG. 9 is an end view of the FIG. 8 conveyor.

FIG. 10 is a top view of the FIG. 8 conveyor.

FIG. 11 is a side view of the FIG. 8 conveyor.

FIG. 12 is a front view of a preferred roller assembly of the presentinvention.

FIG. 13 is a side view of the roller assembly of FIG. 12.

SUMMARY OF THE INVENTION

The present invention allows for the utilization of a wide range of rawmaterials, previously considered economically and technicallyunfeasible, to produce various products made from recycled materials andwhich are of acceptable quality for numerous end uses. Furthermore, inmany instances, the present invention makes possible the creation of amultiplicity of products with attributes superior to those ofconventionally manufactured products.

By the present invention, wood fiber is identified, decontaminated,sized and dried, as appropriate, to achieve a moisture content of lessthan about 15% by weight. Also, waste plastic material, such as HDPE andLDPE, is identified, cleaned and dried.

The wood fiber is then mixed with the waste plastic material in a rangeof ratios from about 40% plastic/60% fiber to about 60% plastic/40%fiber by weight, with a 45% plastic/55% fiber mix preferred. The plasticcomponent of the mix may be 100% of one type of plastic or may be acontrolled blend of plastics, such as 60% LDPE/40% HDPE by weight blend.

The mix is then mixed, heated and kneaded to a temperature high enoughto melt the plastic and enable the melted plastic to encapsulate thewood fiber particles. This temperature is defined as the encapsulationpoint.

The mix is then fed to a material preparation auger, where it is cutinto small chunks suitable for use as a feed to an extruder.

The chunks are then fed to an extruder and formed into a product havingvarious cross sections in accordance with the cross section of a diechosen for use with the extruder. The temperature of the product ismaintained by various means.

After extrusion, the product is cut into desired lengths, inspected,rolled, cooled, collected and then either subjected to furtherprocessing or assembled for shipment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

With reference to the general process steps used to produce thesynthetic wood products of the present invention, as well as withreference to examples in which specific starting materials and specificprocessing parameters are set forth, preferred embodiments of thepresent invention will be described.

In preferred embodiments of the present invention waste wood fiber andwaste plastic are reclaimed and processed into various synthetic woodproducts such as, for example, building materials, including roofshingles, siding, floor tiles, paneling, moldings, structuralcomponents, steps, door and window sills and sashes; house and gardenitems, such as planters, flower pots, landscape tiles, decking, outdoorfurniture, fencing and playground equipment; farm and ranch items,including pasture fencing, posts and barn components; and marine items,for example, decking, bulkheads and pilings.

STEP 1

The first step in the process is the identification and collection ofwood fiber starting materials, preferably waste wood materials such ascedar fiber. Once identified and collected, the waste wood startingmaterial is placed into a holding bin or storage area.

Although other wood fibers may be used, cedar fiber is the preferredwood fiber for the present invention. Cedar fiber, as envisioned withinthe scope of the invention, is presently available as a waste productfrom cedar oil mills. Raw waste from cedar oil mills usually includescedar fiber contaminated with rocks, metal and relatively large chunksof wood, all of which must be removed from the raw cedar fiber wasteprior to placing the desired cedar fiber waste into a holding bin.

In addition to the other wood fibers being usable as a startingmaterial, mixtures of cedar fiber and other wood fibers may be used as astarting material.

STEP 2

Once identified, the cedar fiber raw feed material is processed toremove contaminants. The preferred decontamination equipment includesscreens, shakers, separators and magnets to remove various foreignmaterials such as stones, metal and large pieces of wood.

All of the decontamination equipment envisioned for use in the presentinvention are conventional and their use is well known for the statedfunctions.

In addition to using magnets to remove metallic contaminants found inthe raw cedar fiber feed material, or other raw wood fiber feed, it ispreferred that additional magnets be used at various locationsthroughout the processing system for the purpose of removing pieces ofmetal which might break away from processing apparatus or otherwisebecome a contaminant during processing.

STEP 3

After contaminant removal, the cedar fiber is subjected to conventionalgrinders, such as hammermills, and vibrating screens in order to producea processed fiber feed having maximum size characteristics. Thepreferred maximum diameter of the wood fiber is one-eighth inch, and,thus, screens sized to yield minus one-eighth inch diameter fibers arepreferred. Since much of the wood fiber is in the form of slivers, thescreens will allow the passage of fibers having lengths greater than themaximum allowed diameter. The preferred fiber length is less than oneinch.

STEP 4 (Proposed)

At this point in the process, it is preferred that the cedar fiber havea certain maximum moisture content by weight. For further processing,the moisture content of the cedar fiber should not exceed about 15% byweight and it is preferred that the moisture content of the cedar fiberbe less than about 12% by weight.

It has been found that cedar fiber from cedar oil mills typically hasabout 15% to 30% moisture by weight, although this percentage can behigher, depending on the circumstances of the cedar oil mill processingand weather conditions, such as relative humidity, recent rainfall, etc.

The moisture content of the cedar fiber may be reduced at differenttimes and/or locations. For example, the cedar fiber may be dried at thecedar oil mills prior to delivery to the synthetic wood productmanufacturing site. In such event, the cedar fiber is dried by means ofa conventional dryer to a moisture content of less then 15% by weight.

However, because cedar fiber, like other wood fiber, is hygroscopic andtends to pick up moisture the more it is handled and the longer it isheld after being subjected to a drying procedure, it is envisioned thata preferred drying step take place at this stage of the process.

A conventional, variable speed in-line wood dryer fueled by waste woodchips or other fuel may be used to reduce the moisture content of thecedar fibers. It is envisioned that any conventional equipment may beused so long as the function of effectively reducing the moisturecontent of the sized cedar fibers, or their equivalent, is accomplished.It is also envisioned that microwave technology may be used to flashsteam off from the sized cedar fiber to achieve the desired moisturecontent reduction.

The objective of reducing moisture content to less than approximately15% by weight at this step is considered important because it has beendiscovered that excessive moisture in the cedar fiber material willcause pitting or bubbling in the finished product.

Thus, whatever the identification of the wood product raw feed materialis, it is important to reduce the moisture content to a level which willavoid the problems of pitting or bubbling in the finished product.

STEP 5

The sized, and heat treated, as appropriate, cedar fiber is thenconveyed by conventional means, such as a bucket elevator, to aconventional holding bin or storage area.

STEP 6

In parallel with the identification and preliminary processing of thewood fiber, a corresponding identification and preliminary processing ofwaste plastic material is accomplished.

First, waste plastic raw materials are identified, collected and placedinto conventional holding bins. Presently, it is envisioned that highdensity polyethylene (HDPE) and low density polyethylene (LDPE) are thepreferred types of waste plastic materials.

HDPE has a density of greater than approximately 0.94 g/cc, measured inaccordance with ASTM D1505, and a melt index of less than approximately1.0 g/10 minutes, measured in accordance with ASTM D1238, Condition190/2.16. An example of such type material is Marlex polyethylene, resinnumber EHM 6007, manufactured by Phillips 66, Bartlesville, Okla.

LDPE has a density of less than approximately 0.94 g/cc, measured inaccordance with ASTM D1505, and a melt index of greater thanapproximately 1.0 g/10 minutes, measured in accordance with ASTM D1238,Condition 190/2.16. An example of such type material is Polyethylene5004 extrusion coating resin manufactured by The Dow Chemical Company,Midland, Mich.

Preferably, the waste plastic materials are segregated into differentholding bins according to type.

Numerous sources of waste LDPE and HDPE are available and it isenvisioned that waste plastics from any of these sources may be used inthe present invention. Also, it is envisioned that other types ofplastics may be used within the scope of the present invention. Otherplastics which may be considered equivalent for purposes of the presentinvention are those which can be processed with extrusion equipment ofthe type disclosed herein and at temperatures which would not adverselyaffect the wood fiber feed component in terms of producing unacceptableproduct for a desired end use. Also, of course, any plastic having theappropriate temperature and physical properties must also be relativelyinert in that it must be approved for use in environments in which theend product is used, as well as in the manufacturing environment.

Preferred sources of LDPE are floor sweepings from conventionalpetrochemical plants, commonly referred to as sump LDPE. Sump LDPE isknown to have some polypropylene material contaminant mixed in with itand this contaminant has not adversely effected the end productsproduced with the process of the present invention. Also, "off spec"LDPE purchased as waste product from petrochemical plants is anotherpreferred source of LDPE.

It is envisioned that another source of LDPE will be plastic lining fromcertain food packaging operations and beverage container operations, aswell as other types of plastic coated papers. It is known that the paperin such plastic coated paper items may be recycled through a process inwhich the paper and plastic are separated from each other, i.e.,hydropulping. It has been found that the LDPE resulting fromhydropulping is acceptable as a plastic feed material for the currentinvention so long as the residual paper content is not excessive, thatis, does not exceed about 10% by weight.

Preferred sources of HDPE are articles manufactured from HDPE, such ascommonly produced containers for milk, distilled water, fruit juices,soft drink concentrates, liquid detergents, bleach, etc. Also, "offspec" HDPE purchased as waste product from petrochemical plants isanother preferred source of HDPE.

STEP 7

The raw plastic material feed is then cleaned, if necessary, to removeunwanted foreign or contaminant material. The contamination removal stepemploys conventional screens, shakers, magnets and washing equipment, asis well known. Even though it is believed that most sources of LDPE andHDPE are essentially contaminant free, it is preferred that, as aprecaution, all plastic feed material introduced into the process besubjected to cleaning or contaminant removal.

STEP 8

The cleaned plastic feed material is then dried to remove any residualmoisture from the aforementioned washing procedure. The dried plasticfeed material preferably has 0% moisture content by weight, however,trace amounts of moisture may remain with the dried plastic feedmaterial without significantly adversely affecting subsequent processingsteps. The preferred drying operation is accomplished throughconventional use of a conventional, vertical, in-line spin air dryer.

STEP 9

The dried plastic feed material is then conveyed to holding bins andclassified into various bins according to each type of plastic feedmaterial.

STEP 10

Treated fiber from Step 5 and treated plastic from Step 9 are thenweighed in accordance with a desired, predetermined mix ratio byintroducing such fiber and plastic into a hopper equipped with scalesfor determining the weight of each component. Conventional means, suchas screw conveyors or bucket elevators, may be used to convey the woodfiber and plastic material from their holding bins to the hopper.

The preferred ratio of the cedar fiber to plastic in the mix is 45%plastic and 55% fiber, by weight. It has been found that the rangeswithin which usable product may be achieved are from about 40% plasticand 60% fiber to about 60% plastic and 40% fiber by weight.

The particular mixture of ingredients is chosen as a function of thecharacteristics of the final product desired, the type of plastic andtype of fiber chosen. For example, in a preferred mix formulation, 100%LDPE is used as the 45% plastic component and 100% cedar fiber as the55% wood component. In another preferred mix formulation, a 60/40 blendby weight of LDPE and HDPE, respectively, is used as the 45% plasticcomponent and 100% cedar fiber as the 55% wood component.

During the step of preparing the mixture, the fiber and plastic may befed to the hopper in any order. For example, if a 55% fiber to 45%plastic mix is desired, 550 lbs. of fiber could be added to the hopper,then 450 lbs. of plastic could be added, or vice versa.

After the entire weight of fiber and plastic is conveyed to the hopper,then the entire weight, in this example 1000 lbs., would be dischargedfor further processing in accordance with the present invention.

In this example, if the plastic were totally LDPE, 450 lbs. of LDPEwould be added to the hopper. If the plastic were 60% LDPE and 40% HDPE,then 270 lbs. of LDPE and 180 lbs. of HDPE would be added to the hopper.

It has been found that a relatively stronger end product can be producedby inclusion of HDPE in the mix formulation. For example, when theproducts made with the two preferred mix formulations mentioned above,i.e., the first with 100% LDPE plastic and the second with the 60LDPE/40 HDPE plastic blend, are compared from the force required to pulla screw from each type, approximately 42% more lbs. force is required topull a screw out of the product containing HDPE than to pull anidentical screw, identically mounted, out of the product containing allLDPE as its plastic component.

STEP 11

After weighing the desired amounts of fiber and plastic to achieve thepredetermined mix and total weight desired, the mixture in the hopper isunloaded and discharged into a conventional, cleated belt conveyor to abatch holding bin.

STEP 12

From the holding bin the cedar fiber and plastic mix are gravity fedthrough a chute into a conventional compounding machine for heating,mixing and kneading. Although numerous conventional machines may beutilized, the preferred compounding machine is a modified sigma blade,double arm mixer which is insulated and jacketed for heating with hotoil up to temperatures of about 500° F.

The processing objectives to be met within the compounding machine areto heat the fiber/plastic mixture to a temperature high enough to meltthe plastic and to thoroughly mix the wood fiber with the molten plasticso that the molten plastic will bond with and encapsulate the woodfiber. As mentioned earlier, this temperature is defined as theencapsulation point. This processing step yields a homogeneous masshaving the consistency of a ball or lump of sticky cookie dough.

Depending upon the plastic or combination of plastics chosen, theencapsulation point to which the fiber plastic mixture should be raisedwithin the compounding machine will vary. For instance, if the plasticis comprised of only LPDE, the temperature of the fiber/plastic mixtureshould be raised to approximately 310° F. If the plastic is comprised of60% LDPE and 40% HDPE, the mixture should be raised to approximately350° F.

In practice, the oil in the jacket of the compounding machine is heatedto within the range of approximately 400° F. to 500° F., preferably 450°F., prior to introduction of the fiber/plastic mixture. Then thefiber/plastic mixture is introduced into the compounding machine and thetemperature of the fiber/plastic mixture is monitored until it reachedthe desired level, at which time the mixture is discharged from thecompounding machine.

Because different fiber/plastic mixtures must be heated to differentencapsulation points to achieve adequate processing within thecompounding machine, processing time within the compounding machinevaries. Generally, with all other factors being constant, the higher theencapsulation point, the longer the processing time will be.

STEP 13

After processing in the compounding machine, the bonded fiber/plasticmixture is then conveyed from the compounding machine to a heatedmixture holding bin by conventional means such as a cleated beltconveyor.

The holding bin is heated by conventional means and maintains themixture in a hot, malleable state.

The heated mixture holding bin level can be automatically controlled byconventional means and the temperature of the bin and its mixture ismaintained by a conventional hot oil jacket system. The heated mixtureholding bin is maintained at a temperature sufficient to keep thematerial within its proper processing temperature and consistency range.This range will vary depending upon the make-up of the mixture itself.For instance, if the mixture is 55% fiber and 45% plastic, with thefiber being solely cedar fiber and the plastic being solely LDPE, thetemperature range is preferably 280° F. to 320° F. If the mixture is 55%fiber and 45% plastic, with the fiber being solely cedar fiber, but withthe plastic being a blend of 60 parts LDPE and 40 parts HDPE, thetemperature range is preferably 320° F. to 360° F.

If the mixture cools below a certain lower limit, which will varyaccording to mixture, it will not extrude properly in a subsequentProcessing step. Also, the mixture must not be permitted to rise to atemperature above a certain maximum temperature, which will also varyaccording to the mixture, because the mixture will not extrude properlyin a subsequent processing step. For a 55% cedar fiber/45% LDPE mixture,this minimum temperature is approximately 250° F. and the maximumtemperature is approximately 350° F. For a 55% cedar fiber/45% plasticblend with 60 parts LDPE and 40 parts HDPE, the minimum temperature isapproximately 290° F. and the maximum temperature is approximately 390°F.

STEP 14

The mixture is then fed from the holding bin to a material preparationauger which forms the mixture into chunks, preferably approximately thesize of golf balls. With reference to the preferred material preparationauger, as illustrated in FIGS. 1-3, hot fiber/plastic mixture is fedfrom the heated holding bin by means of gravity through a chute into thematerial preparation auger 20 near its upstream end 22.

The mixture is then moved toward the downstream end 24 of the materialpreparation auger housing 26 by the rotation of the material preparationauger shafts 28, 30 which have a plurality of material preparation augerblades 32 attached thereto. An individual blade 32 is illustrated inFIG. 3. The shafts 28, 30 are rotated inwardly by conventional meanssuch as a motor, not illustrated. The action of the blades on themixture sizes the mixture into pieces approximately the size of golfballs as the material is moved toward the downstream end 24 of thematerial preparation auger housing 26. These pieces of mixture aredischarged from the material preparation auger through the dischargeopening 34 in the bottom of the material preparation auger housing nearits downstream end and conveyed to the extruder.

The shafts have a plurality of blades 32 affixed thereto. The first fewupstream blades 32, approximately three, on each shaft are mounted at anangle of approximately 15° to the direction of travel of the mixture.The remaining blades are mounted at an angle of approximately 30° tothis direction. The material preparation auger performs the function ofcreating a uniformly-sized feed stock for use in downstream extrudingequipment. This feed stock can be introduced into the extruder at aconsistent rate to minimize surging during the extrusion process.

STEP 15

The uniformly sized chunks of feed stock are then conveyed to acompounding extruder 36, as shown in FIG. 4, preferably by means of aconventional 12" diameter screw conveyor.

Although the preferred conveying means is a 12" diameter screw conveyor,it is believed that a cleated belt conveyor may be used for thispurpose. It is believed that a cleated belt conveyor may be advantageousin that it will reduce residue within the conveyor which otherwise couldharden and contaminate subsequent batches of malleable fiber/plasticmixture.

Although, as presently practiced, the preferred process feeds chunks ofmalleable material directly to an extruder 36, it is envisioned that aconventional compounding roll mill may be incorporated into the system.Prior to the extruder so that other material, such as a fire retardant,U.V. stabilizers, strength inducers, compatibilizers, engineered resinsand other substances having advantageous properties may be introducedinto the mixture prior to extrusion.

STEP 16

The mixture is extruded through a predetermined die and formed into aproduct having a predetermined configuration.

The preferred extruder 36 is a standard compounding extruder, having abarrel tapered from a 12" diameter to a 6" diameter , and powered by a40 hp, 800 rpm electric motor. The extruder has been modified so thatits barrel and screw have been shortened to 36" and it has been equippedwith a water jacket 38, with port 40 for cooling the mixture duringextrusion.

It has been discovered that cooling is required to prevent the mixturefrom becoming too hot as it is extruded due to the friction and sheercreated by the mixture as it is forced through the extruder. A mixtureof 55% cedar fiber and 45% LDPE should not be allowed to reach atemperature of greater than approximately 450° F. at this stage. Asimilar mixture with the plastic component of 60 parts LDPE and 40 partsHDPE should not be allowed to reach a temperature greater thanapproximately 500° F. at this stage. These mixtures have a tendency toignite when their respective stated temperatures are exceeded.

With reference to FIG. 4, the extruder 36 is equipped with a bolster 42and interchangeable dies, one of which, die 44, is shown, whereby theproduct profile configuration may be changed upon changing the dies. Thebolster 42 which holds the die is equipped with electrical heatingelements not shown, which pass through ports 46 for use in heating thedie during extrusion. It is important that the surface temperature ofthe mixture must be sufficiently high at the point where the mixtureexits the extruder 36 to create a uniform surface for the extrudedproduct. If proper surface temperature is not maintained, the surface ofthe mixture may tear as it exits the extruder die.

In some cases additional heat is required at the dies and thisadditional heat is provided by the heating elements on the bolster. Thepreferred surface temperature at the exit of the extruder isapproximately 425°-450° F. for a 55% cedar fiber/45% LDPE mixture and450°-475° F. for a similar mixture with a plastic component of 60 partsLDPE and 40 parts HDPE. Temperature sensors are placed inside thebolster through ports 48.

During operation of the extruder 36, fiber/plastic mixture is introducedinto the mixture inlet 50 of the extruder 36.

The mixture is forced through the extruder barrel outlet 52 by means ofa conventional screw mechanism within the extruder driven by aconventional motor and gear mechanism, not shown, within the motor andgear housing 54.

The mixture exits the extruder barrel through the extruder barrel outlet52. The extruder housing and extruder barrel are water jacketed forcooling as shown at 38.

As the mixture exits the extruder barrel it is forced, in turn, throughthe fiber alignment plate 56, the extruder bolster 42 and then theextruder die 44. The fiber alignment plate 56 has the configurationshown in FIG. 4 so that it will function to straighten out and align themixture for passage through the bolster 42 and die 44. It has been foundthat without the fiber alignment plate 56, tis mixture has a tendency toretain the orientation given it by the extruder screw and not maintainproper alignment as it passes through the die.

The fiber alignment plate 56 configuration shown is the preferredconfiguration for extrusion of a 55% cedar fiber/45% LPDE mixture, aswell as a similar mixture with the plastic component thereof comprisedof 60 parts LPDE and 40 parts HDPE. It is envisioned that the fiberalignment plate configuration may be varied for other fiber/plasticformulations.

The bolster 42 holds and supports interchangeable dies 44 for theextrusion of desired products having different profiles orconfigurations. The bolster 42 also has heating element ports 46 for theinsertion of heating elements, not shown, so that the mixture may beheated as it exits the die 44. These heating element ports 46 arepreferably provided so that separate heating elements may be insertedand controlled proximate the top, bottom and both sides of the die tofacilitate uniform heating of the die.

The bolster is also provided with temperature sensor ports 48 for theinsertion of temperature sensors, such as conventional thermocouples, sothat the temperature of the bolster may be monitored and controlled.

The extruder die 44 is affixed within a recess 56 in the downstream endof the bolster. The die 44 shown forms the mixture into an L-shapedconfiguration as the mixture is forced therethrough. The die ispreferably comprised of two separate components, a top half 58 and abottom half 60 for ease of insertion into and extraction from theextruder bolster 42.

STEP 17

The extruded product is cut into desired lengths as it exits theextruder 36. The cutting operation is performed by a custom flyingcutoff assembly 62 as shown in FIG. 5-7, equipped with an electric eyesensing device 64.

As product 90 is forced out of the extruder 36, it slides continuouslyand successively onto and across the entry tray 66 of the flying cutoffknife assembly 62, the product support plate 68 of said assembly, andthe exit tray 70 of said assembly. The product then slides onto theconveyor belt 72 of the inspection table assembly 74.

An adjustable electric eye sensing device 64 is provided on theinspection table 76 so that when a leading edge of product is sensed bythe device 64, a signal is transmitted to a processor which activatesthe two air cylinders, 78, 84 as further described. Assuming that theknife 80 of the flying cutoff knife assembly is in the down position, isshown in FIG. 6, the air cylinder 78 attached to the knife is activatedto move upwardly so that the product is severed by the upper cuttingedge 82 of the steel knife 80. Simultaneously, the horizontal aircylinder 84 of the assembly 62 is activated to move the flying cutoffknife housing in the direction of the flow of product at the same speedat which the product is moving. This allows the product to be cut intopieces while it is continuously flowing from the extruder without thepiece of product on the upstream side of the knife blade ramming intothe blade as a cut is being effectuated.

Once a cut is completed, the piston of the horizontal air cylinder 84retracts, returning the flying cutoff knife housing 86 to its startingposition.

As is shown in the end view drawings, FIGS. 6 and 7, a product opening88 is provided in the flying cutoff knife 80 so that product cancontinue, to flow through the flying cutoff knife housing while theknife is in its up position. When the knife is in such up position asshown in FIG. 7, the next product cut is made by the lower cutting edge90 of the knife 80 when the void between the trailing edge of the mostrecently cut piece of product and the immediately following leading edgeof the product stream is sensed by the sensing device 64 and theattached processor activates the air cylinder 78 attached to the knife80 to return the knife 80 to its down position shown in FIG. 6. Ofcourse, at the same time, the processor activates the horizontal aircylinder 84 to move the flying cutoff knife housing 86 as describedabove for the upward stroke of the knife 80.

This procedure is then continued for as many product cuts as desired.

As also shown in FIG. 5, product 92 is shown positioned within theflying cutoff knife assembly 62 and on inspection table 76. The assembly62 has a housing 86, side frame 92, top frame 94, product stop blockscrew 96, product support plate screw 98, and bottom frame 100. Productguide 102 is positioned to guide the product 90 and has guide rod holder104 and guide rod holder support 106 connected thereto. Cylinder 84 ismounted at mount 108 and has piston 110. The assembly 62 is movablealong shaft 112 on linear ball cage bearing 114 between urethane bumpers116, 118. The inspection table assembly 122 includes the table 76,conveyor belt roller 124, and belt tensioner 126.

Referring to FIGS. 6 and 7, the piston 128 for cylinder 78 is shown inFIG. 7. Shown in FIG. 6 is product support plate 130 and adjustableproduct guide rod 132, product guide 134, with metal brace, made of UHMWplastic or Teflon coated material. Also shown is blade guide 136,product stop block 136, guide clamp 138, product exit tray 140, knifeholder 142, shaft support 144, horizontal support frame 146, back stopplate 148, leg 150 and base 152.

With regard to the operation of the flying cutoff knife the followingitems should be noted:

(a) Preferably the product guides 134 and the product entry tray 66 andexit tray 140 are constructed of UHMW plastic or Teflon coated materialto facilitate the sliding of the product thereacross.

(b) The exit port of the extruder 120 is aligned with the entry tray 66,support plate and exit tray 140 of the knife housing assembly which arein turn aligned with the top of the inspection table 76 so that theproduct moves in a straight line.

(c) The product stop block 136 holds the product 90 in place as theknife is moved upwardly through the product. It has been found that thisis desirable since at the cutting stage the product is pliable and has atendency to bend as it is being cut. The product support plate 130performs the same function when the knife is cutting in the downwarddirection.

(d) The product support plate 130 has a slot therein to allow forpassage of the knife therethrough.

(e) The speed at which the flying cutoff knife housing 86 moveshorizontally is adjustable so that varying speeds of product flow can beaccommodated.

(f) The electric eye sensor 64 on the inspection table 76 is adjustableso that the lengths of the product being cut may be varied as desired.

(g) The speed of the conveyor belt on the inspection table is preferablymaintained at a speed approximately 15% faster than the flow rate of theproduct so that cut pieces cf product will be moved away from theproduct stream at a rate faster than the flow rate of the product streamitself.

(h) An activation switch, not shown, preferably provided on a footpedal, is provided to allow a person at the inspection table to cutproduct before it reaches a pre-set length. This allows for a shorterlength of product to be rejected if a defect is noticed in the productthereby reducing waste from the process.

STEP 18

The cut lengths of hot product 90 are then conveyed by conventionalmeans, such as a belt conveyor, across an inspection table and sent to acustom rolling and cooling conveyor.

At the inspection table, any reject material is removed from theprocess.

STEP 19

Acceptable, hot extruded product 90 is then passed through anadjustable, variable speed rolling and cooling conveyor 154, asillustrated in FIGS. 8-13. The rolling and cooling conveyor 154functions to maintain the profile configuration of the lengths of hot,extruded product 90 in their predetermined configuration so as to avoiddeformation upon cooling. The guides 156 and rollers 158 of the rollingand cooling conveyor 154 may be adjusted to accommodate differentproduct configurations. Of importance in the particular application ofthe present invention, the pressure exerted by the rolling and coolingconveyor on the hot, extruded product 90 is held to a minimum so thatthe hot product will cool and contract substantially independently ofpressure exerted by the conveyor. It has been found that if pressure isexerted on the product at this stage by the conveyor, stresses can beinduced into the product and the final product weakened.

Referring to FIGS. 7-9, operation of the rolling and cooling conveyorwill be described. The product is conveyed from the inspection table 122to the first set of rollers 158 of the rolling and cooling conveyor 122.The bottom rollers 160 of the conveyor are turned by a chain drivemechanism powered by a conventional power source, preferably a variablespeed electric motor 162.

The bottom rollers 160 convey the product through the conveyor assemblyfor a distance sufficient to allow the product to cool to a temperatureat which the product is adequately cured for handling, i.e., less than180° F. The speed of the rollers may be varied to conform with the speedof the conveyor belt on the inspection table so that a continuous flowof product pieces may be maintained. The distance of conveyor travel foradequate cooling varies with atmospheric conditions, speed of therollers and configuration of the product. In practice, it is preferredto provide for excess travel so that one is assured that the product hasadequately cooled. For an L-shaped product configuration made up of 1.5lbs./ft. of mixture, it has been found that 200 feet of travel at aroller speed of 30 ft./min. is sufficient for adequate cooling.

The side view FIG. 8 of a section of the rolling and cooling conveyorshows ten roller assemblies. Counting from left to right, the first,third, fifth, seventh and ninth roller assemblies move the productpieces in a rightwardly direction. As will be explained, the directionof the product pieces is reversed and the tenth, eighth, sixth, fourthand second roller assemblies move the product pieces in the leftwardlydirection.

To reverse the direction of the pieces of product, a reversing table 164is provided as shown in FIGS. 10 and 11. The reversing table 164 isequipped with powered rollers 166 as shown in the side and top views ofFIGS. 11 and 10, respectively, as well as an electric eye sensing device168 and a product ram 170. When the device senses a product piece whichis being conveyed in the rightwardly direction in FIG. 10, a signal istransmitted to a processor which activates the air cylinders 172 of theproduct ram 170 which extends to push the product pieces onto opposite,flanged rollers which move the product pieces in the opposite direction.

Sections of conveyor and reversing tables may be assembled as requiredin an area which would not accommodate a straight-line conveyor toprovide enough conveying distance for proper product cooling.

Once cooled, the product pieces exit the last section of the conveyorfor further processing or shipment.

With regard to the operation of the rolling and cooling conveyor, thefollowing items should be noted:

(a) The roller assemblies are adjustable to accommodate product piecesof differing thickness. Also, the rollers may be interchanged toaccommodate product pieces having different configurations.

(b) The conveyor is equipped with product guides 174 to facilitateproper alignment of the product pieces as they are being conveyed. Theproduct guides are preferably constructed of UHMW or Teflon coatedmaterial to reduce frictional resistance between the product pieces andguides as they come in contact during the movement of the productpieces.

(c) The rollers are knurled, as shown in FIG. 12, preferably with acoarse, knurled pattern. It has been found that this makes the rollersself-cleaning and reduces the amount of contact surface between theproduct pieces and the rollers, thereby facilitating the cooling of theproduct pieces.

Referring to FIG. 8, the conveyor 154 is shown having chain drive 178,idler sprocket 180, idler sprocket mount 182 and support bearing 184.

Referring to FIG. 9, the conveyor 156 has gear box 186, chain 178, shaftsupport bearing 184, drive sprocket 190, driven sprocket 192, bottom:frame 196, shaft 194, guide rod 198, guide rod holder support 200, guiderod holder 210, guide clamp 212, product guide 174, bracket 214, idlersprocket 216, side frame 218, leg 220, and adjustable pad 222.

Referring to FIGS. 10 and 11, the reversing table 164 is also shownhaving air cylinder 172, electric eye sensor 168, ram 170, drive chain224, bottom frame slat 226, and ram guide rod 228.

Referring to FIGS. 12 and 13, the roller assembly is also shown asincluding adjustable top roller supports 230 having threaded adjustablesleeves 232, adjusting screws 234 and lock nuts 236. The top rollers 237are provided with top roller flanges 238, top roller sizing segments240, and top roller knurl sections 242. Roller bearing 244 and rollerlocking collars 246 also support rollers 237. Bottom knurled rollers 248are supported on shafts 250 and have locking collars 252 positioned asshown. Top rollers 237 rotate around shafts 254 as shown in FIG. 13.

STEP 20

After cooling, the lengths of product are collected and assembled forshipment or further processing, such as sawing, machining, painting andforming into desired products such as previously mentioned. Such furtherprocessing may also include milling and finishing operations forpurposes such as smoothing the surface areas of the lengths and addingfeatures such as grooves and/or slots to the product.

EXAMPLES

In accordance with the above described process steps, the followingexamples are set forth below to illustrate specific processes, specificstarting materials, specific processing parameters and specific blendsof plastic/wood starting materials.

EXAMPLE 1

In accordance with the steps outlined above, a 1000 lb. batch of mixturehaving 550 lbs. of cedar fiber of an 8% moisture content and 450 lbs. ofLDPE plastic was made.

This mixture was dumped and conveyed to a compounding machine in whichthe hot oil jacket temperature was approximately 475° F. The initialinside wall temperature of the compounding machine was approximately410° F. The mixture was kept in the compounding machine forapproximately 1 hour and then transferred to a heated holding bin. Thesurface temperature of the material at the time it was transferred tothe holding bin was approximately 310° F.

The mixture was processed through the material preparation auger andthen transferred to the extruder and extruded into a product having anL-shaped configuration as shown in FIG. 4. In this particular example,the configuration resulted in a product yield of one and one-half lbs.per foot of extruded product. The speed of the extruder was set atapproximately 25 lbs. per minute. The barrel of the extruder was cooledby means of a water jacket so that the temperature of the barrel did notexceed approximately 250° F. The extruder pressure was maintained atapproximately 500 psi. The extruder die temperature was maintained atapproximately 725° F. by means of the electrical heating elements in thedie bolster. The surface temperature of the mixture as it exited fromthe extruder was approximately 430° F.

After exiting the extruder, the hot product was then cut into lengths of5 feet, inspected and then passed through the rolling and coolingconveyor equipment where it was cooled to room temperature.

EXAMPLE 2

In accordance with the steps outlined above, a 1000 lb. batch of mixturehaving 550 lbs. of cedar fiber of a 7% moisture content and 450 lbs. ofa plastic blend comprising 270 lbs. of LDPE and 180 lbs. of HDPE wasmade.

This mixture was dumped and conveyed to a compounding machine in whichthe hot oil jacket temperature was approximately 475° F. The initialinside wall temperature of the compounding machine was approximately410° F. The mixture was kept in the compounding machine forapproximately 11/2 hours and then transferred to a heated holding bin.The surface temperature of the material at the time it was transferredto the holding bin was approximately 350° F.

The mixture was processed through the material preparation auger thentransferred to the extruder and extruded into a product having anL-shaped configuration as shown in FIG. 4. In this particular example,the configuration resulted in a product yield of one and one half lbs.per foot of extruded product. The speed of the extruder was set atapproximately 25 lbs. per minute. The barrel of the extruder was cooledby means of a water jacket so that the temperature of the barrel did notexceed approximately 250° F. The extruder pressure was maintained atapproximately 500 psi. The extruder die temperature was maintained atapproximately 725° F. by means of the electrical heating elements in thedie bolster. The surface temperature of the mixture as it exited fromthe extruder was approximately 450° F.

After exiting the extruder, the hot product was then cut into lengths of5 feet, inspected and then passed through the rolling and coolingequipment where it was cooled to room temperature.

VARIATIONS IN PROCESSING STEPS

There may be some variation in the process depending on a number ofcircumstances. For example, if the extruder die is changed to produce aproduct profile having an increased yield in terms of lbs. per foot, therolling and cooling conveyor equipment downstream must be adjusted, thatis, its speed must be reduced to accommodate a slower through-put interms of feet per minute of product, assuming that the extruder speed isheld constant. On the other hand, with a constant extruder speed, if adie is chosen so that the yield is fewer lbs. per foot, then the speedof the downstream equipment must be increased correspondingly.

It is envisioned that numerous alternate processing steps and alternateembodiments of the present invention may be envisioned by one ofordinary skill in the art. It is intended that all such alternatives andalternate embodiments are included within the scope of the presentinvention which is defined by the hereby appended claims.

We claim:
 1. A conveyor having a plurality of upper roller assemblies, aplurality of lower roller assemblies, and means for rotating the lowerrollers at a desired speed, each upper roller assembly furthercomprising a transverse shaft rotatably mounted at each end thereof in abearing member supported by an adjustable roller support member havingupper and lower ends; each adjustable roller support member comprisingthe lower end releasably connected to the bearing member, and threadedmeans for selectively adjusting the distance between the upper and lowerends; and at least one roller disposed on the shaft.
 2. The conveyor ofclaim 1 wherein each lower roller assembly comprises at least one rollerand each upper roller assembly comprises at least one roller selectivelyspaced a desired distance above at least one roller of each lower rollerassembly.
 3. The conveyor of claim 2 wherein at least one roller of eachupper roller assembly has a roller flange having a diameter greater thanthe distance between the shaft and at least one roller of each lowerroller assembly.
 4. The conveyor of claim 1 wherein each adjustableroller support member comprises a locking means for the threadedadjustment means.